rust-lang / rust-lang/rust-clippy

Clippy suggests broken code in explicit_counter_loop lint

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C-bug
Dominant language
Rust
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Description

Running cargo clippy on this:

fn main() {
	let mut arr = [0; 10];
	let mut counter = 0;
	for i in 0..arr.len() {
		arr[i] = counter;
		counter += 1;
	}
}

Clippy suggests changing it to:

fn main() {
	let mut arr = [0; 10];
	let mut counter = 0;
	for (counter, i) in (0..arr.len()).enumerate() {
		arr[i] = counter;
		counter += 1;
	}
}

Which doesn't compile.

> cargo clippy --version
clippy 0.1.89 (2eef47813f 2025-05-22)
> cargo --version
cargo 1.89.0-nightly (47c911e9e 2025-05-14)
> rustc --version
rustc 1.89.0-nightly (2eef47813 2025-05-22)

Contributor guide

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First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Reproduce the report with the supplied Rust example and cargo clippy, then locate the explicit_counter_loop lint implementation and its tests. Check the generated suggestion against the compiler; done means the suggested code compiles and preserves the loop's behavior.

Written by the indexing model from the issue text.

Assessment

Tech stack
rust
Domain
tooling
Issue type
Bug
Difficulty
3/5
Estimated time
1-2 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
48/100

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